1. Field of the Invention
This invention relates to devices and methods used for reducing and/or eliminating the tubular vortices commonly produced by rotating blades in aeronautical applications, as well as those produced by aircraft wings during flight, specifically to a spoiler made from flexible material having an irregularly-configured freely projecting distal edge that is primarily contemplated for use in eliminating the ‘pop-pop’ sound one hears when a helicopter main rotor is moving at speed. Elimination of such noise will provide a stealth capability to helicopters that has never before been experienced. Thus, a helicopter would be able to enter a conflict zone, and not have a hostile force anticipate its arrival solely as a result of the repetitive popping noise so familiar to everyone who has ever been within the audible proximity of a helicopter in flight. It is preferred for the spoiler to be flap-like, with a thin and flat configuration that hangs loosely or projects freely from its attached proximal surface. It is also preferred for the present invention spoiler to be made from supple, resilient, and durable non-ferrous material, such as rubber, a rubber-like material, plastic, rubber impregnated with thin steel mesh, canvas reinforced rubber, rubber composites, and other durable materials that do not prematurely fatigue as a result of repeated contact with high-speed air movement around them, and are capable of vibrating or oscillating like a stretched rubber band in the wind. Further, the material used for the present invention spoiler must be able to withstand shocks without premature deformation or rupture. It is contemplated for the resiliency of the material used for the most preferred embodiment of the present invention spoiler to be similar to that used for the mud flaps on a semi-truck. Alternative descriptions of the needed spoiler movement for the purposes of this disclosure, and which collectively give one a better understanding of the type of action taking place, are shuttering, quivering, beating, trembling, pulsating, resonating, fluttering, flapping, singing, and/or the ready ability to move quickly in up and down directions without permanent deformation or fatigue. The preferred means of connecting the present invention spoiler to the trailing edges of rotor blades, airfoils, and propellers, although not limited thereto, involves the use of one or more pre-machined grooves close to that trailing edge, one or more mounting plates, bolts, rivets, and/or adhesive. Redundant attachment methods are preferred to maintain the present invention spoiler in place on the trailing edge while it undergoes high-speed oscillation. When the spoiler material becomes worn and is no longer able to fulfill its vortex eliminating function, substitution with a replacement present invention spoiler is contemplated and easily accomplished as a part of routine maintenance procedures. It is further contemplated for the freely projecting distal edge of the present invention spoiler to have a non-repeating pattern of angular indentations which creates therebetween a plurality of feather-like projections with differing shape and pitch that bend with resistance and/or vibrate without deformation to collectively break up vortex formation as it tries to occur. When the formation of tubular vortices is prevented at the trailing edge of a blade or aircraft wing, the noise and vibration commonly experienced in aircraft operation is significantly reduced, as the next wing or blade traveling through the same location has clean air/fluid in which to move. Thus planes can follow one another more closely during flight, and as applied in helicopter applications, the prevention of vortices by the present invention spoiler also prevents the typical ‘pop-pop’ sound associated with helicopter flight that results from collapse of the vortices created during the revolution of each blade and the leading edge of the next adjacent blade coming into contact with the resulting turbulence as it is washed rearward from its predecessor. Further, in addition to noise reduction, the common helicopter problem of rotor vibration, for which extensive research to reduce it has been previously conducted, is considerably reduced by use of the present invention spoiler. It absorbs blade vibration by resisting the sympathetic airframe vibration transferred from the engine to the blades. As vibration can generate great heat that prematurely destroys copper gaskets and many sealant compounds, use of the present invention spoiler to reduce vibration would obviate the need for such replacement and provide the added benefit of reduced maintenance cost. A further benefit of noise reduction is a quieter cabin for passengers and crew. In addition to noise and vibration reduction, the capability of the present invention spoiler to eliminate tubular vortices from the trailing edges of blades and airfoils also provides increased rotor and propeller efficiency, and increased wing/airfoil lift.
2. Description of the Related Art
While movie productions have fantasized about noiseless helicopter flight, in modern helicopter flight, a repetitive ‘pop-pop’ sound is commonly heard as the main rotor blades and tail rotor blades of gasoline-powered and turbine-powered helicopters rotate. It is the blade tips traveling at terminal velocity that create this popping sound. The turbine blades in turbine-powered helicopters similarly produce noise. While such helicopter noise contributes to the noise pollution in urban areas, the ‘pop-pop’ sound presents a significant problem in hostile environments, as by announcing the arrival of the helicopter in advance it makes the helicopter more vulnerable to attack. Further, as previously mentioned, vibration in helicopters is a common problem, significantly contributing to operator and parts fatigue. Some examples of dampers currently used to reduce helicopter vibration, are the Westland Flexspring vibration absorbers, the Bifilers pendulum, and containers filled with mercury. All can be eliminated by use of the present invention, with significant operational cost reduction. In addition, the decreased weight of a helicopter when these types of dampening devices are eliminated permits increased payload, and with respect to the use of mercury, the potential hazard of a mercury spill in the event of a mishap is also eliminated. Use of the present invention spoiler in aircraft can also eliminate the cost of flapping hinges, articulated shock absorbers, and specially designed rotor tips. In addition to noise reduction, rotor vibration is also considerably reduced, as well as lift and blade retard. There are no known spoiler modifications to propellers and aircraft wings having the same structure and features as the present invention, nor all of its advantages.